DIY Ribbon Construction - STEELE

[Andrew Steele]

Hi everyone - These are some ribbon speakers I am in the progress of building - They are really in a prototyping stage right now - experimenting with ribbon thickness, rear chamber stuffing etc.. - I have designed the motor so I can adjust the gap from 20mm down to 5mm - I have no transformer yet so I'm just using resistors to make measurements (very inefficient) The plan is to keep this thread updated as progress is made.


Current Specs:
Magnets: Neo N40 4"x1/2"x1/2"
Ribbon size: 20mm x 100mm

[Andrew Steele]

Primary Test results - taken @ 0.5m

[george a]

Hi Andrew

May I ask where you obtained your magets ? nd for how much ? -I am also in the land of OZ and finding neos at a sensible price is difficult.
AS you seem to have access to FR measuring equipment, could I suggest doing a comparison with pleated diaphrams (see my earlier post at

http://www.diyaudio.com/forums/showt...20#post1420220

for a quick and dirty method to produce them.

I am considering making a pair similar to those you have and am concerned at the affect of stuffing in the enclosure.

From my experiments my ribbons seems to sound best with no enclosure behind - some absorption to cut down bouncing off the walls can help though.

Also - ribbon material- not knowing what thicknesses are avaialbel ready I took the approach of assuming that the cheapest and nastiest kitchen foil would most ikely be the thinnest. To this end I'm using "Black and Gold" from one of the supermarkets.
What did you use?

Cheers
george

[Andrew Steele]

Hi George A

That's funny because I'm currently using Home Brand foil - noticed how thin it is- I'm thinking between 15um down to 9um - I'm going to try to figure out what thickness it is today by dividing the cu/m weight of aluminium by say a 1m x 30cm long peice of the foil with some accurate scales I picked up today.

-I know what you mean about prices in Australia, the land of the greedy importer/distributor -

As for the magnet source I grabbed mine from:
http://www.magnet4less.com/index.php?ref=90&cPath=1

I thought I'd just attach my order so you could see prices/shipping.
14 x 4" x 1/2" x 1/2" Thick, Grade N42, Ni-Cu-Ni Plated Neodymium Block Magnet (NB075-3) = $70.00
4 x 2" x 1/2" x 1/2" Thick, Grade N45, Ni-Cu-Ni Plated Neodymium Block Magnet (NB054) = $10.56
1 x Magnet Pole Detector - Identifier (POLE-1) = $24.99
24 x 1/2" x 1/8" x 1/4" Rare Earth Neodymium NdFeB Block Magnets, Grade N42 (NB015) = $3.12
------------------------------------------------------
Sub-Total: $108.67
USPS Canada & International Flat Rate (Small International Priority Mail Box: Estimated Transit 7 - 14 Days *Read Disclaimer): $43.95
Total: $152.62


A month ago I set up a thread trying to get some sources listed for cheap neo magnets - have a look at the feedback so-far:
Good/cheap neodymium magnet sources

I'll try to get some measurments going - but I'd really like to get a good transformer on the ribbon before doing so. But I guess no harm in trying with resistors?

PS. I sent you a P.M.

Cheers

Andrew

[Andrew Steele]

Ok - correct me if I'm wrong...

weighed some Home Brand foil - 0.4m2 worth = 10g

which = 25g/m2

Aluminium weighs around 2700kg/m3

so 1um is 0.001mm or 0.000001m

add it all together and 1um aluminium is 2.7g/m2

divide the foil "g/m2" by 2.7 to get the thickness


HomeBrand Aluminium Foil = 9.2um


Still a bit thick as I would like to find under 5um, RAAL ribbons use 4um

Also, I read halving thickness/weight of the ribbon increases efficiency by 6dB

[bear]

Consider measuring with a flush planar baffle on all 4 sides - no gaps (will effect the extreme HF) - that will tell you another story about the response compared to free air.

Also, consider the purpose of the corrugations found in most ribbon speakers - perhaps you want to add some? It might be sufficient to add just one or two on the ends...

Nice looking work.

Consider using the closeup feature on ur digital camera, the image is a bit fuzzy... but it looks good.

_-_-bear

[Few]

You might try cutting open a capacitor if you want a source of thinner aluminum foil. That's worked well for others.
Few

[tinitus]

Originally posted by bear

Also, consider the purpose of the corrugations found in most ribbon speakers - perhaps you want to add some? It might be sufficient to add just one or two on the ends...

Corrugation tames most of rattling noise
Mine will be pressured onto a fine zigzag pattern

Nice project

[Andrew Steele]

I have to be honest the progress so far was just me hooking it up to check if the magnetic motor worked - while I was there I thought I'd do some tests while I was there. I have to get a baffle set-up going and corrugations are planned.

The fuzzy picture is couresy of the iPhone and it's lack of any autofocus. I'll take some better pictures soon - When I've sorted a better ribbon mounting setup as there's no real point now.

Few - I bought a bunch of capacitors to try to some thin foil but all the different types I got were thicker than aluminium foil. I got low voltage, high voltage, low capitance and high capitance - all the same. Anyone got tips on what capacitors have the right foil?


Cheers
Andrew

[Andrew Steele]

OK, had some time to build a proper mounting system, put some small pleats in the ribbon - take a look.